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From: Ravi Pandya <ravip@netmanage.com>
Subject: Re: Object Technology: What will JAVA do that Smalltalk won't do?
Message-ID: <NEWTNews.813944281.8284.ravip@ravip3.netmanage.com>
Date: Tue, 17 Oct 95 08:33:40 PDT
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In Article<45788j$mes@ftp.netgate.net>, <tmh@possibility.com> writes:
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> From: Todd Hoff <tmh@possibility.com>
> Newsgroups: comp.lang.smalltalk,comp.object
> Subject: Re: Object Technology: What will JAVA do that Smalltalk won't do?
> Date: 8 Oct 1995 01:07:31 GMT
> Organization: Possibiliyt Outpost, Inc.
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> 
> David N. Smith <dnsmith@watson.ibm.com> wrote:
> >In article <454ouv$gpa@ftp.netgate.net> Todd Hoff, tmh@possibility.com
> >writes:
> >>Most (all?) Smalltalks do not have true separately scheduable
> >>threads in the image. They mostly just start a thread, do a job,
> >>and return. 
> >
> >Huh? Smalltalk, since BlueBook days, has had forkable processes,
> >priorties, semaphores, etc., and the system itself uses them. 
> >
> 
> Process != thread. Processes on most systems cannot share the same 
> memory space. And forking processes is the heaviest method of 
> getting multiprocessing we have. Not acceptable in my book for a 
> modern language on modern systems. Constipating execution via a 
> single threaded image is almost criminal on MP machines.
> 
All "processes" in Smalltalk run in the same memory environment - they all 
have direct access to the same set of objects. They correspond to what an OS 
would call threads. There is in fact nothing in Smalltalk corresponding to an 
OS process with memory protection, etc. However, I don't believe any of the 
commercial Smalltalks will map these onto OS threads so that they can take 
advantage of MP - it's all done through the Smalltalk virtual machine. In 
VisualWorks, you can take a look at all of this by poking around inside 
Processor, ProcessorScheduler, etc.

Ravi Pandya
NetManage
ravip@netmanage.com


